Nice piece Lofty.
The handle has the bottom silver missing but I'm sure that you should be able to do something about that. The arrangement of the rings looks original as the silver wire linking them does not appear loose. My guess is definately not Omani as there is no typical scroll decoration. I would guess at either Saudi or Yemeni but from the proximity of the Omani border.
As far as the blade is concerned, if there is not rust, just a light rub with an oiled cloth so as not to remove the patina.
Stu